[Ffmpeg-devel] [PATCH] Snow mmx+sse2 asm optimizations

[Michael Niedermayer]

Hi

On Tue, Mar 07, 2006 at 07:07:06PM -0500, Robert Edele wrote:
> On Tue, 2006-03-07 at 15:34 -0800, Loren Merritt wrote:
> > On Tue, 7 Mar 2006, Robert Edele wrote:
> > > On Mon, 2006-03-06 at 02:06 +0100, Michael Niedermayer wrote:
> > >> On Sun, Mar 05, 2006 at 06:09:09PM -0500, Robert Edele wrote:
> > >>> +        ::
> > >>> +        "m"(b0),"m"(b1),"m"(b2),"m"(b3),"m"(b4),"m"(b5),"d"(end_w2):
> > >>> +        "%"REG_a"","%"REG_b"","%"REG_c"");
> > >>
> > >> this code is not valid, REG_d is changed but neither output nor on the clobber list
> > >
> > > REG_d is on the input list, so GCC recognizes it as clobbered? GCC
> > > also refuses that I put it REG_d into the clobber list. I believe the
> > > code is good as is?
> > 
> > If it's both input and clobbered, put it on the output list with "+d".
> 
> Putting "+d"(end_w2) pr "=d"(end_w2) in the output list causes the
> program to crash. 

well, you will have to debug it i fear if you want to see the code in cvs


> The variable is not used after the asm block.

maybe not at the C level but at the asm level gcc is free to use the register
and unless you mark it as changed u MUST gurantee that it didnt change
these are the rules of gcc asm, you can look it up in the gcc manual
page or some introduction to gcc asm (try google)

[...]

-- 
Michael